Microevolution

• populations evolve, not individuals

• populations evolve through genes

Allele - Two+ variant forms of one gene (1 father, 1 mother)

Phenotype - observable traits

gene pool - made up of all the allele’s that exist in a population

Evolution - any change in allele frequencies of a gene pool over time

Micro-evolution - change of allele frequencies in a population (gene pool) over short period of time

Fitness - Success passing genes to offspring, relative to other members in population “Survival of the fittest”

Causes for microevolution:

Mutation

• any permanent alteration in an organisms DNA

• occurs due to DNA replication errors/environmental factors

• must occur in the DNA of the Gametes (sex cells)

• occurs randomly

• extremely important (only way new genetic material comes about)

Gene Flow

• movement of genes from one population to another due to migration

• to change allele frequency in a population, new members must create a different gene pool

• quite common in nature

Natural Selection

• process in which the fit of an organism with its environment selects those traits that will be passed on with greater frequency from one generation to the next

• only agent that adapts populations to their environment

• regarded as the most important agent in shaping the natural world

Genetic Drift

• chance event that alters gene (allele) frequency in a population cuts lives short at random

• greatest impact on small populations

  1. Bottleneck Effect - occurs following a sharp reduction in a population size

  2. Founder Effect - small population migrates to a new area to start a new population

Coevolution

• interdependent evolution of the two or more species

• predator - prey interactions (camouflage, chemical warfare)

• Mullerian Mimicy - several species that have protection against predators evolve to resemble each other

• Bayesian Mimicry - evolution of one species to resemble another that has superior protective capability

• symbiosis

Sexual Selection

• acts on traits that help an animal acquire a mate

• driven by contests among males or female preference

Genetic Diversity

• gene pools benefit from diversity

• diverse gene pool prevents loss of an entire population after environmental change

• significant health problems with inbred & artificially selected individuals

• diverse MHC genes aid the immune system in identifying invaders

3 Modes of Natural Selection

1. Directional Selection - Natural selection promotes the extreme version of one trait favorably over the other at a large rate

2. stabilizing selection - intermediate forms of a given character or trait are favored over extremes

3. Disruptive Selection - natural selection favoring both extremes (can eventually lead to macroevolution)